in Planetary Science Did Sulfur Affect Mars Climate and Geology? Mars missions suggest that Mars once had a thick CO 2 atmosphere and liquid water On Earth these conditions lead to formation of carbonate rocks (like limestone) But Mars missions detect very little carbonate rock; instead Mars rovers find sulfate rocks This rock outcrop studied by the Opportunity rover, contains the sulfur-bearing mineral jarosite. The inset shows a close-up of a hematite ‘blueberry’ believed to form due to water. 1.3 cm ~30 cm

in Planetary Science Volcanoes on Earth and Mars spewed out CO 2 and SO 2 along with H 2 O Why does Mars have more sulfur-rich rocks? On Earth Volcanic SO 2 rapidly reacts with oxygen and water vapor CO 2 absorbed in water, forms carbonate rocks Little CO 2 left in our atmosphere - just enough for a mild greenhouse effect On Ancient Mars Less oxygen and water vapor in atmosphere, so some SO 2 absorbed in surface water Water too acidic for carbonate formation, CO 2 stays in atmosphere Sulfur-bearing minerals form in water and make sulfate rocks The White cliffs of Dover, composed of carbonate Endurance Crater, Mars, with countless ‘blueberries’ formed due to acidic liquid water

in Planetary Science The Big Picture Sulfur gases may have affected the geology and climate of Mars enough to make it habitable in the past. A minor gas (SO 2 ) can radically change Mars chemistry, preventing the major gas (CO 2 ) from forming carbonate rock as on Earth CO 2 in the atmosphere (instead of in rocks) plus H 2 O and SO 2 gases provided lots of greenhouse warming for ancient Mars Planetary scientists continue to investigate why the paths of these two planets diverged billions of years ago

in Planetary Science For more details… Press Releases Marsdaily.com - 12/24/07 - “ How Mars Could Have Been Warm And Wet But Limestone-Free ” Marsdaily.com - 12/24/07 - “ Sulfur Dioxide May Have Helped Maintain A Warm Early Mars ” Images El Capitan and blueberry images courtesy of NASA/JPL White cliffs of Dover image: Blueberries in Endurance Crater image courtesy of NASA/JPL Volcanic eruption diagram Adapted from “The Cosmic Perspective”, by Bennett et al., Addison Wesley, Inc. Mars & Earth composite image courtesy of NASA/JPL Source Article (on-campus login may be required to access journals) Halevy et al., ‘A Sulfur Dioxide Climate Feedback on Early Mars’, Science, 318, 1903 (2007), DOI: /science Prepared for the Division for Planetary Sciences of the American Astronomical Society by David Brain and Nick Schneider Released 14 April 2009